The role uses [apt_repository module](http://docs.ansible.com/apt_repository_module.html) which has additional dependencies. I highly recommend to use [bootstrap-debian](https://github.com/cederberg/ansible-bootstrap-debian) role to setup common Ansible requirements on Debian-based systems.

You can use `default_release` option for [apt module](http://docs.ansible.com/apt_module.html) to install package from backports. For example: